In the design of compact optical instruments such as cameras a primary goal is the minimization of the required distance between an objective lens and an image focal plane while maximizing the size of the image produced thereon. Various types of single lenses and lens combinations have been designed in an attempt to achieve this goal but these suffer from the drawback of relatively high cost and the introduction of significant distortion in the produced image. One example of a prior art lens combination is disclosed in U.S. Pat. No. 3,784,277.
Lenslet arrays are well known in the art for producing an array of small images. It is also known in the art from U.S. Pat. Nos. 3,459,111 and 3,950,769, to use a lenslet array and an aperture mask to produce a dissected image on photosensitive film held at the plane of the aperture mask. When the procedure is reversed and the image on the film is illuminated from the rear and projected onto a viewing screen the image is reconstructed. The purpose of such a system is to produce a plurality of composite images on a single frame of photosensitive materials. This is possible because the film is in the plane of the aperture mask and it necessitates the use of apertures large enough to be resolved by the film.
Such lenslet arrays have hitherto not been proposed for use in solving the above problem of maximizing image size while minimizing the required separation of the lens from the image plane, producing a directly viewable image without the necessity of decoding or projection, due to the fact that they produce a plurality of small images rather than a single large image.